Researchers at RTI International, Center for Health, Analytics and Media and Policy, RTI International, and Office of Research Protection, Research Triangle Park, North Carolina, conducted the driver study. The results were published online on April 23, and will be published in Preventive Medicine ReportsJune 20, 2222

This study examined 1,249 people’s consumption habits. One third of the participants said they drove under the influence in less than three hours after getting high. Another third reported that cannabis was used within the past 30 days.

“Current cannabis users in recreational and medical-only cannabis states were significantly less likely to report driving within three hours of getting high in the past 30 days, compared to current users living in states without legal cannabis,” researchers wrote. “The one exception was frequent cannabis users who lived in medical cannabis states. They are at risk for DUIC [driving under the influence of cannabis] did not differ significantly from frequent users living in states without legal cannabis.”

Researchers suggest a solution for driving under the effects of marijuana, and it should target specific states with no legal cannabis programs. “Our findings suggest that DUIC prevention is most needed in states without legalized cannabis. Because regulation of cannabis products in non-legal environments is not possible, mass media campaigns may be a good option for providing education about DUIC.” 

Researchers concluded that education campaigns can help prevent drivers from using cannabis to induce impairment. “Although all states should educate its citizens about the potential dangers of using cannabis and driving, this analysis suggests that states without legal cannabis are particularly in need of DUIC prevention efforts,” they wrote. “States should consider mass media campaigns as a method of reaching all cannabis users, including more frequent users, with information about the dangers of DUIC. Medical states may consider targeting frequent users by disseminating information about DUIC through medical dispensaries.”

This study shared the findings of three others that also mirrored these results. One was published in 2021 and two of them were shared in 2020. They both used different approaches to examine the impact of medical and recreational cannabis legalization.

NORML’s Deputy Director Paul Armentano commented on the results of this study with the hope that it will educate those who fear the negative effects of cannabis legalization. “These findings ought to reassure those who feared that legalization might inadvertently be associated with relaxed attitudes toward driving under the influence,” said Armentano. “These conclusions show that this has not been the case and that, in fact, consumers residing in legal marijuana states are less likely to engage in this behavior than are those residing in states where cannabis possession remains criminalized.”

Massachusetts is one of the states that are increasing enforcement of impaired driving laws. Governor Charlie Baker announced legislation in November 2021 that would “provide law enforcement officers with more rigorous drug detection training and will strengthen the legal process by authorizing the courts to acknowledge that the active ingredient in marijuana can and does impair motorists.” However, Baker’s legislation does not address how to approach measuring impairment or properly identifying if a person has recently consumed cannabis and is impaired, or if they consumed days or weeks before an incident and are no longer impaired. 

Recent Canadian research reveals the importance of a more accurate way to identify impairment. “We would love to have that one measure that says, okay, this person is impaired, or they aren’t,” said lead author Sarah Windle. “But unfortunately, in the case of cannabis, it just isn’t that simple.”